The present invention relates to a printer beam and more particularly to a structural beam for supporting a slider rod upon which slides a printhead carriage.
It is a well-known need in printers to be able to keep constant the distance between the printhead and the print medium, the so-called xe2x80x9cpen to paperxe2x80x9d spacing. If this distance varies, the dots are not printed accurately and the print quality deteriorates. To achieve this object, it is essential to keep the slider rod or rods as straight as possible.
One previous proposal to solve this problem is to use a beam of extruded aluminium and to accurately machine V-shaped grooves along its length to support two slider rods. Such a beam is disclosed in co-pending European patent application 99301172.5. However, such beams are relatively expensive to manufacture, and the machining operation is time-consuming. The slider rods are usually made of steel and so problems can also arise with respect to differential thermal expansion.
Another previous proposal, for example as disclosed in U.S. Pat. No. 5,195,836, is to mount the slider rods on the beam by means of a plurality of individually adjustable bridges. Again such methods of assembly are expensive and time consuming.
The present invention seeks to overcome or reduce one or more of the above problems.
According to a first aspect of the present invention, there is provided a method of manufacturing a hardcopy apparatus support comprising the steps of fixing a plurality of support elements at spaced intervals in a substantially straight line on a beam member, machining precisely aligned faces in portions of the support elements spaced from the beam member, and mounting and securing a slider rod to said faces.
Each support element may have a generally V-shaped groove precisely machined therein. In a modification, each support element has a single precisely machined face.
According to a second aspect of the present invention, there is provided a support member for a hardcopy apparatus carriage comprising a beam member, at least one slider rod and means for securing the rod to the beam member, characterised in that said securing means comprises a plurality of support elements fixed at spaced intervals in a substantially straight line on the beam member, said support elements having machined therein, at portions spaced from the beam member, mutually precisely aligned faces.
An advantage of the above support member is that deviations in straightness of the beam member do not affect the straightness of the slider rod.
In preferred embodiments the slider rod and the beam member are of the same material. This avoids any deterioration in print quality brought about by differential thermal expansion. The material is preferably steel, which is relatively inexpensive.
Preferably the support elements are made of a different material from the beam member. Because a relatively small amount of material is needed for the support elements a more expensive material can be used. Also a material chosen for its suitability for being machined can be selected. In preferred embodiments, the support elements are made of brass.